Plugs and Wires

In the UK, electrical appliances connect to the mains electricity with a three-pin plug. Each pin has a wire with a unique colour, which makes it easy to identify.

The features of a plug are shown below.

Each wire is made from copper, so it can conduct electricity. For safety, they are coated in a layer of insulating plastic. Let’s look at an actual plug:

The table below highlights the properties of each of the 3 wires.

LiveCarries the alternating potential difference from the power supply.Brown
NeutralTakes the electric current back to the source to complete the circuit.Blue
EarthThis is the safety wire.

There can be an electrical fault in the circuit, which could happen when the live wire loosens and touches the casing.

To prevent this, the Earth wire gives the current an alternative path to flow, which also prevents the appliance from operating.
Green and yellow

As you can see in the table below, the potential difference between the live wire and both the neutral wire and the earth wire is 230 V.

WiresPotential difference between them (V)
Live and neutral230
Live and earth230
Neutral and earth0

The current is able to flow into the neutral wire and earth wire because the potential difference between them is 230 volts. The human body is typically at 0 V, which makes the live wire very dangerous, as there is a large potential difference between the live wire and the human body. So, the large current can flow through us to the earth, giving us a large electric shock.